A Multi-Source Co-Simulation Method for the Thermal Stability of GaAs Sub-6G Power Amplifier with Adjustable Bias Current

In this paper, the thermal stability of GaAs heterojunction bipolar transistor (HBT) power amplifier (PA) in a sub-6G band has been improved by a multi-source co-simulation method. To reduce the parameter errors caused by the variations of thermal resistances, a co-simulation method for the multiple heat sources of fully-integrated PA is proposed. Specifically, an adjustable bias circuit is applied on the PA for temperature compensation using a zero-to-absolute-temperature (ZTAT) current. To verify the proposed method, a sub-6G PA is realized in the GaAs HBT process. The experimental results show that the variations in power added efficiency and output power is stabilized due to the 3.5% error ZTAT current. The errors between simulation and measurement are reduced from 6% to 1%. According to the thermal factor defined in co-simulation, the working temperature decreases 10 °C, while the area only increases 27%. The above results prove that that thermal stability and the simulation reliability can be co-designed with the minimal area cost.